The present invention relates to an apparatus for simultaneously subjecting a plurality of material test specimens to cyclical tension loading to determine the fatigue strength limit of the material.
When specifying a particular material for a specific application, it becomes important to know the various material characteristics of the materials available. Typically, the materials are run through a battery of tests to determine these characteristics. One such characteristic which is often tested is the fatigue strength of the material.
Determining the fatigue strength of the material entails subjecting a representative specimen of the material to cyclical tension loading until the specimen breaks. The limiting stress created by the tension loading at which the specimen breaks is the fatigue strength limit of the material. In order to achieve an accurate statistical evaluation, a large number of specimens are tested.
Normally, testing of the material is accomplished by testing one specimen at a time in a conventional fatigue testing apparatus. This can be a very time consuming process as each specimen has to be tested one by one. Various devices have been patented which enable several specimens to be tested at one time. One such device was patented in U.S. Pat. No. 3,491,586, granted to Branger, which discloses a fatigue testing apparatus for subjecting a plurality of test specimens to alternating tension and compression loads through use of hydraulically actuated cylinders. Another such device was patented in U.S. Pat. No. 4,030,348, granted to Fletcher et al., which discloses a machine for use in monitoring fatigue life for the plurality of elastomeric specimens through use of a reciprocating drive train. Still another multiple specimen fatigue testing device was patented in U.S. Pat. No. 3,937,071, granted to Slota et al., which discloses the use of a plurality of test stations each having an air actuated tensioning piston attached to a test specimen. While the above patented devices may perform satisfactorily, they are relatively complex in configuration.
Accordingly, an object of the present invention is to provide a device for simultaneously subjecting a plurality of test specimens to cyclical tension loading which is relatively simple in configuration.
Another object of the present invention is to provide a device and method for simultaneously subjecting a plurality of test specimens to cyclical tension loading which, upon the breaking of a specimen, allows for the cyclical tension loading of the remaining specimens to be substantially unchanged and continued.
Still another object of the present invention is to provide a device for simultaneously subjecting a plurality of test specimens to cyclical tension loading which applies substantially equal tension loads to all of the specimens being tested.